.\" Copyright (c) 2004 Apple Computer, Inc.
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.\" Portions of this text are reprinted and reproduced in electronic form
.\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
.\" Portable Operating System Interface (POSIX), The Open Group Base
.\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
.\" Electrical and Electronics Engineers, Inc and The Open Group.  In the
.\" event of any discrepancy between this version and the original IEEE and
.\" The Open Group Standard, the original IEEE and The Open Group Standard is
.\" the referee document.  The original Standard can be obtained online at
.\"	http://www.opengroup.org/unix/online.html.
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.\" $FreeBSD$
.\"
.Dd June 21, 2004
.Dt PTHREAD_ATFORK 3
.Os
.Sh NAME
.Nm pthread_atfork
.Nd register handlers to be called before and after
.Fn fork
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fo pthread_atfork
.Fa "void \*[lp]*prepare\*[rp]\*[lp]void\*[rp]"
.Fa "void \*[lp]*parent\*[rp]\*[lp]void\*[rp]"
.Fa "void \*[lp]*child\*[rp]\*[lp]void\*[rp]"
.Fc
.Sh DESCRIPTION
The
.Fn pthread_atfork
function declares fork handlers to be called before and after
.Xr fork 2 ,
in the context of the thread that called
.Xr fork 2 .
.Pp
The handlers registered with
.Fn pthread_atfork
are called at the moments in time described below:
.Bl -tag -width ".Fa prepare"
.It Fa prepare
Before
.Xr fork 2
processing commences in the parent process.
If more than one
.Fa prepare
handler is registered they will be called in the opposite order
they were registered.
.It Fa parent
After
.Xr fork 2
completes in the parent process.
If more than one
.Fa parent
handler is registered they will be called in the same order
they were registered.
.It Fa child
After
.Xr fork 2
processing completes in the child process.
If more than one
.Fa child
handler is registered they will be called in the same order
they were registered.
.El
.Pp
If no handling is desired at one or more of these three points,
a null pointer may be passed as the corresponding fork handler.
.Pp
.Em Important :
only async-signal-safe functions are allowed on the child side of
.Fn fork .
See
.Xr sigaction 2
for details.
.Sh RETURN VALUES
If successful, the
.Fn pthread_atfork
function will return zero.
Otherwise an error number will be returned to indicate the error.
.Sh ERRORS
The
.Fn pthread_atfork
function will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
The system lacked the necessary resources to add another handler to the list.
.El
.Sh SEE ALSO
.Xr fork 2 ,
.Xr pthread 3
.Sh STANDARDS
The
.Fn pthread_atfork
conforms to
.St -p1003.1-96 .
